1. Field of the Invention
The present invention relates to a dust detection system that detects dust adhering to an imaging device mounted in a photographing apparatus such as a digital camera, based on a photographed image.
2. Description of the Related Art
In a digital camera allowing the interchange of lenses, such as a single-lens reflex camera, dust may accidentally come into the camera body when a lens is removed from the body. Dust entering the body may adhere to the imaging device or a filter on the imaging device. When such dust adheres, it may appear in a photographed image.
Even if dust is visible in a photographed image, some of the dust may be invisible on direct visual inspection. Japanese Unexamined Patent Publication No. 2005-341381 proposes a digital camera which determines whether such dust is attached. The user is encouraged to remove the dust through a warning if dust is detected.
In the manufacturing process of an imaging device or during the mounting an imaging device in a camera body, minute flaws may be generated on the infrared cut filter or the low-pass filter, or minute dust may come between such filters. It is difficult to remove such minute flaws and dust after manufacturing. Accordingly, if a flaw or dust is visible in a photographed image on quality check of a camera after manufacturing, the camera fails inspection.
Sufficiently minute flaws and dust are invisible in a photographed image and are not problematic. However, images of such flaws and dust are exaggerated by the edge-enhancement signal processing in the dust-detecting function in the above patent publication, allowing the user to recognize the flaw or dust. Because such flaws and dust cannot be removed, as mentioned above, it is undesirable for the user to detect them even after cleaning the filter or imaging device.